In the processing of textile yarns to form fabrics, it has been conventional to apply a protective sizing composition to the yarns prior to fabric formation, such as weaving, in order to keep the yarns from being abraded and damaged during the fabric formation operations. Starches, polyvinyl alcohol, polyacrylates, polyacrylamides, and polyesters are some of the compositions which have been typically used as sizing compositions.
After the fabric is formed, it is conventionally subjected to a desizing operation to remove the sizing composition prior to bleaching, dyeing, and finishing. The desizing step has been necessary because the presence of the sizing composition on the yarns interferes with the bleaching, dyeing and finishing operations, and if not removed would adversely affect final aesthetic properties of the fabric. The desizing operation is an undesired extra step in textile processing which introduces additional processing time and expense. Additionally, because of the expense of the sizing compositions, as well as governmental regulations on waste water quality, desizing operations may require expensive reclamation or treatment facilities to reclaim the sizing composition and remove it from the waste water, or to treat the waste water to make it pure enough to discharge.
It has been previously recognized that it would be desirable to have a sizing composition which could be permanently applied to yarns, and which would therefore avoid the need for desizing and the attendant time and expense involved in size reclamation. Although there has been considerable interest in the development of a permanent sizing composition, the prior attempts to provide such a composition have been generally unsuccessful. In order to be acceptable for use in commercial production, a permanent sizing composition must meet a number of exacting criteria. The composition must be applied using conventional textile slashing equipment and must serve the intended functions of a yarn size during formation of the fabric. Furthermore, it must not be removed by or chemically degraded by caustic scouring operations, bleaching, mercerizing, dyeing, and fabric finishing processes. Also, the sizing composition which is present on the yarns must be fully compatible with conventional dyes and finishing agents so that the fabric may be dyed and finished using conventional dyes and production processes. In addition, it must meet all of the foregoing criteria without conferring undesirable fabric aesthetics or inferior fabric physical properties.
Prior attempts known to applicants at producing a permanent sizing process and composition have failed to satisfy the foregoing exacting criteria and have therefore not been acceptable for use in commercial operations, except perhaps in certain very specialized applications. Typically, the prior approaches have involved attempts to use conventional non-durable sizing agents, and to cause them to become permanently bound to the yarn through the use of a crosslinking agent. This approach is described, for example, in U.S. Pat. Nos. 3,676,207 and 3,666,400, and in European patent application No. 57,985.